1. Technical Field
The present disclosure is generally directed to compositions and methods for the delivery of polynucleotides, more particularly to compositions and methods for transfection, for example transfection of organelles.
2. Related Art
Many mitochondrial diseases have been described that arise from single homoplasmic mutations in mitochondrial DNA (mtDNA). These diseases typically affect non-mitotic tissues (brain, retina, muscle), present with variable phenotypes, can appear sporadically and are untreatable. Evolving evidence implicates mtDNA abnormalities in diseases such as Parkinson's and type II diabetes, but specific causal mutations for these conditions remain to be defined. Understanding the mtDNA genotype-phenotype relationships and developing specific treatment for mtDNA-based diseases is hampered by inability to manipulate the mitochondrial genome.
In the course of evolution, many organisms tackled the task of introducing macromolecules into living cells. Aside from the cell-specific, usually receptor-mediated or active uptake mechanisms, the general solution that has independently emerged in many lineages relies on peptides specifically evolved to interact with, and insert into lipid bilayer membranes. Thus, bacterial colicins, human porins, and protein transduction domains (PTDs) from diverse species share the motif of a positively charged alpha-helix, frequently with an amphipathic structure, which is capable of inserting into lipid membranes, and delivering larger cargoes intracellularly. Recent research reports confirm the successful use of PTDs fused to proteins for their delivery across biological boundaries, including the blood-brain barrier, and the placenta.
Another issue of great importance in the delivery of macromolecules in organisms is the need to protect them from proteolytic, nucleolytic and immune degradation and removal while traversing extracellular spaces. An often used approach is coating DNA with proteins capable of surviving the harsh journey to the target. Viral capsid proteins have been quite successful, yet for the purpose of DNA delivery in humans they suffer from a significant drawback—immunogenicity, the capacity to evoke a strong immune reaction greatly reducing the effectiveness of gene therapy.
Thus, there is a need for improved compositions and methods for the delivery of polynucleotides to the interior of a cell.